1. Field of the Invention
The invention relates generally to process control within chemical reactions. More particularly, the invention relates to enhanced process control within ethylene oxidation chemical reactions.
2. Description of the Related Art
Commercially significant chemical reactions may in general be undertaken using either a batch processing chemical reactor or a continuous processing chemical reactor. Also included as adjunct materials to reactant materials and product materials within many commercially significant chemical reactions are: (1) catalyst materials that facilitate a chemical reaction of a particular reactant material to form a particular product material; (2) promoter materials that are typically incorporated into a particular catalyst material to promote performance of the particular catalyst material with respect to a particular chemical reaction (i.e., where such performance may be optimized with respect to at least a catalyst activity and a catalyst specificity); and (3) moderator materials that are intended to be incorporated within a particular reactant material batch or stream, and to appropriately moderate performance of a particular catalyst material with respect to a particular chemical reaction.
While there are many commercially significant chemical reactions that may be used to produce, in general, large quantities (i.e., thousands of tons per year) of organic chemical intermediate or product materials, inorganic chemical intermediate or product materials and hybrid organic and inorganic chemical intermediate or product materials, a particularly fundamental commercially significant chemical reaction is a chemical oxidation reaction (i.e., chemical epoxidation reaction) of ethylene with oxygen to form ethylene oxide (i.e., ethylene epoxide). In turn, the ethylene oxide that is formed from the foregoing chemical oxidation reaction may be hydrolyzed to form ethylene glycols which further comprise yet another commercially significant organic chemical product material and/or organic chemical intermediate material.
Commercially significant ethylene oxide production through the silver based catalyzed reaction of ethylene with molecular oxygen within a multi-tubular continuous reactor has been well known, productively used and incrementally improved for many decades. Notwithstanding the foregoing, due to the extraordinary volumes of scale within commercially significant ethylene oxide production, an otherwise seemingly inconsequential process improvement not yet implemented within commercially significant ethylene oxide production may nonetheless still yield a considerable economic dividend.
Various aspects of the ethylene oxide production through the silver based catalyzed reaction of ethylene and molecular oxygen are known in the chemical processing art. Of special interest is the application of a chloride moderator in this process. For instance R. McNamce, U.S. Pat. No. 2,238,474, disclosed the addition of ethylene dichloride to the ethylene oxidation feed to enhance the catalyst's efficiency.
G. Law, U.S. Pat. No. 2,279,469, disclosed that adding a halogen compound to the feed suppresses the formation of carbon dioxide.
G. Sears, U.S. Pat. No. 2,615,900, disclosed that addition of a metal halide to the silver catalyst reduced the formation of carbon dioxide.
D. Sacken, U.S. Pat. No. 2,765,283, disclosed that washing the carrier, which will be used to prepare ethylene oxide catalyst, with a chlorine containing compound resulted in higher conversion and higher yield
Lauritzen, U.S. Pat. No. 4,874,879, disclosed the prechloriding of fresh Re-containing catalyst before adding oxygen to the feed.
M. Nakajima, U.S. Pat. No. 4,831,162, disclosed a feed that included a “chlorine-containing burning reaction de-accelerator” and an oxide of nitrogen for a highly selective catalyst containing Rb and silver.
T. Notermann, U.S. Pat. No. 4,994,587, and P. Hayden, U.S. Pat. No. 5,387,751, both disclosed a gas feed comprising a chloride moderator and an oxide of nitrogen for high selectivity catalyst.
P. Shankar, U.S. Pat. No. 5,155,242, disclosed that pre-chloriding the fresh catalyst will facilitate the start up of a catalyst containing Cs and silver. It was also disclosed that the pre-chloriding allows the start up of a Re containing catalyst at a lower temperature.
P. Hayden, EP 0057066, disclosed that chlorine containing moderators are of different effectiveness. If the feed contains several moderator compounds the catalyst's performance will be affected by the effective sum of the moderators and not their absolute sum.
Y. Oka, U.S. Pat. No. 6,300,507, disclosed the addition of the chloride moderator in the form of liquid that is injected in the feed steam.
W. Evans, U.S. Pat. Nos. 6,372,925 and 6,717,001, disclosed that for highly selective catalysts, the moderator's concentration has to be optimized repeatedly during the operation, in order to maintain maximum selectivity. Also it was disclosed that a small changes in the moderator's level exhibits pronounced effect on the catalytic performance.
Finally, P. Chipman, U.S. Pat. No. 7,193,094, disclosed that in operating a highly selective silver catalyst, the moderator level is adjusted with the change in reaction temperature.
Also in the open literature Montrasi et al., in “Oxidation of Ethylene to Ethylene Oxide: Role of Organic Chlorides,” Oxidation Communications, Vol. 3 (3-4), 259-67 (1983), teaches an organic chloride moderator material that reversibly influences an activity and a selectivity of a silver based catalyst within a silver based catalyzed reaction of ethylene with molecular oxygen to form ethylene oxide. The moderator level has to be increased in response to a reduced catalyst activity. It was also taught within the foregoing reference that the use of a “chloride scavenger” material allows a wider operative range of the organic chloride moderator material.
Commercially significant chemical reactions, such as in particular ethylene oxidation reactions, are certain to continue to be prominent as domestic and world economies expand. Thus, desirable are methods whereby such commercially significant ethylene oxidation reactions may be efficiently optimized.